Sputtering target with an insulating ring and a gap between the ring and the target

ABSTRACT

A sputtering plasma reactors for plasma vapor deposition (PVD) having an improved interface between a PVD target, a ceramic ring and a PVD chamber wall. The reactor includes a PVD chamber wall and a PVD target, wherein the target in conjunction with the PVD chamber wall form a vacuum chamber and wherein at least the portion of the target facing the vacuum chamber is composed of material to be sputtered. The reactor also includes an insulating ceramic ring positioned between the target and the PVD chamber wall. A first O-ring is provided to establish a vacuum seal between the target and the insulating ring and a second O-ring is provided to establish a vacuum seal between the insulating ring and the PVD chamber wall. At least one spacer is positioned between the target and insulating ring to maintain a gap G between the insulating ring and the target. The spacer is made of a suitable low coefficient of friction material and inhibits black marking, scratching or the like that may otherwise occur along the interface between the ceramic ring and the target.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of application Ser. No.11/884,799, filed Aug. 21, 2007 which is the National Stage ofInternational Application No. PCT/US2006/007062, filed Feb. 28, 2006which claims the benefit of Application 60/656,966, filed Feb. 28, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to sputtering plasma reactors forplasma vapor deposition (PVD), and more particularly, to an improvedinterface between a PVD target, a ceramic ring and a PVD chamber wall inthe plasma reactor.

2. Description of Related Art

In modern fabrication of semiconductor integrated circuits, metals aretypically deposited by physical vapor deposition (PVD) utilizing aplasma reactor. This deposition process is performed in a plasma reactor10 illustrated in the schematic cross section in FIG. 1. The reactor 10includes a target 12, which in conjunction with a PVD chamber wall 14and other sealing members, forms a vacuum chamber 16. The target 12 isfixed to a target backing plate 18, behind which are locatedunillustrated scanning magnets and the chamber cover. At least theportion of the target 12 facing the central portion of the vacuumchamber 16 is composed of the material to be sputtered, which can be,for example, aluminum. A substrate whose surface is to be sputterdeposited is supported on a pedestal (not shown) positioned inopposition to the target 12.

An insulating ring 26 between the target 12 and the PVD chamber wall 14allow their differential biasing. The insulating ring 26 is desirablymade of a ceramic material. A first O-ring 28 establishes a vacuum sealbetween the target 12 and the insulating ring 26 while a second O-ring30 maintains the vacuum seal between the insulating ring 26 and anadapter ring 32 of the PVD chamber wall 14.

A gas supply system (not shown) supplies a controlled flow of variousgases into the vacuum chamber 16 while a vacuum pump maintains a vacuumlevel at a fixed gas flow. The vacuum chamber 16 is filled with argon orother non-reactive gas to a reduced pressure. Note however that in someapplications a reactive gas is additionally filled into the chamber toeffect reactive sputtering. The conductive chamber wall 14, usually madeof aluminum or stainless steel, is generally grounded while a DC powersupply 24 applies a negative voltage of about −500V to the target 12.

The electrical bias causes the argon to discharge and form a plasma ofpositively charged argon ions and negatively charged electrons in thespace between the target 12 and the substrate. The argon ions areelectrically attracted to the negatively charged target 12 and, strikeit at high enough energy to sputter target particles from the target 12.To promote uniform erosion of the target 12, a magnetron may be providedabove the target. However, in some applications the magnetron might beomitted by increasing the energetic electron injection ionization of thehigh density electron cloud 900. A DC power setting for biasing thetarget 12 of 3 kW is preferred but a range of 2-5 kW and a pedestal biasvoltage of −30 volts DC is believed to be satisfactory for manyapplications. The sputtered material travels ballistically, generallyomni-directionally, and some fraction hit the substrate 20 to bedeposited thereon as a thin film.

Current designs typically have the target 12 making direct contact withthe insulating ring 26 located between the PVD chamber wall 14 and thetarget. Direct contact of the target 12 with the insulating ring 26 cancause visible scratches and black marking to occur on the target duringthe sputtering process. As a result, the target 12 needs to beperiodically reconditioned.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to sputtering plasma reactorsfor plasma vapor deposition (PVD). The reactor includes a PVD chamberwall and a PVD target, wherein the target in conjunction with the PVDchamber wall form a vacuum chamber and wherein at least the portion ofthe target facing the vacuum chamber is composed of material to besputtered. The reactor also includes an insulating ceramic ringpositioned between the target and the PVD chamber wall. A first O-ringis provided to establish a vacuum seal between the target 12 and theinsulating ring, and a second O-ring is provided to establish a vacuumseal between the insulating ring and the PVD chamber wall. At least onespacer is positioned between the target and insulating ring to maintaina gap G between the insulating ring and the target. The spacer is madeof a suitable low coefficient of friction material and inhibits blackmarking, scratching or the like that may otherwise occur along theinterface between the ceramic ring and the target.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features of this invention will becomemore apparent and the invention itself will be better understood byreference to the following description of embodiments of the inventiontaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic cross section of a prior art plasma reactor;

FIG. 2A is a schematic cross section of a plasma reactor having a spacerforming a gap between the target and the ceramic ring of the plasmareactor;

FIG. 2B is a schematic plan view of the plasma reactor of FIG. 2A;

FIG. 3 is a schematic cross section of the plasma reactor with analternate embodiment of the spacer;

FIG. 4 is a schematic cross section of the plasma reactor with anotheralternate embodiment of the spacer; and

FIG. 5 is a schematic cross section of the plasma reactor with anotheralternate embodiment of the spacer.

Corresponding reference characters indicate corresponding partsthroughout the views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The invention will now be described in the following detaileddescription with reference to the drawings, wherein preferredembodiments are described in detail to enable practice of the invention.Although the invention is described with reference to these specificpreferred embodiments, it will be understood that the invention is notlimited to these preferred embodiments. But to the contrary, theinvention includes numerous alternatives, modifications and equivalentsas will become apparent from consideration of the following detaileddescription.

FIG. 2A illustrates a cross sectional view of a portion of a PVD plasmareactor 200 incorporating one embodiment of the invention. The reactor200 includes a target 212, which in conjunction with a PVD chamber wall214 and other conventional sealing members, forms a vacuum chamber 216.The target 212 is desirably generally disk-shaped. A substrate (notshown) whose surface is to be sputter deposited is supported on apedestal (not shown) positioned in opposition to the target 212 in aknown configuration. The spacing between the substrate to be sputteredand the target 212 is preferably about 140 mm, but can range from about80 mm to about 200 mm (about 3 inches to about 8 inches).

The target 212 is separated from the PVD chamber wall 214 with aninsulating ring 226. The insulating ring 226, which may be made of avariety of insulative materials, including ceramics, spaces the target212 from the PVD chamber wall 214 so that the target 212 may beadequately negatively biased. A first O-ring 228 establishes a vacuumseal between the target 212 and the insulating ring 226 while a secondO-ring 230 maintains the vacuum seal between the insulating ring 226 andan adapter ring 232 of the PVD chamber wall 214 to provide a vacuumtight assembly for the vacuum chamber 216.

According to the invention, a gap G is maintained between the insulatingring 226 and the target 212 by inserting at least one spacer 240 betweenthe target and insulating ring. In one embodiment, the spacer 240comprises a number of pressure pads located around the outercircumference of the target 212. Each pressure pad 240 is partiallyreceived in a counter bore hole 241 formed in the flange of the target.Desirably, the pressure pads are made of Teflon. However, other plasticmaterials may be used without departing from the scope of the invention.Use of the Teflon or similar low coefficient of friction material willinhibit black marking, scratching and the like that may otherwise occuralong the interface between the ceramic ring 226 and the target 212.

As best seen in FIG. 2B, a plurality of counter bore holes 241 arelocated in the target 212 in a generally circular pattern radiallyoutside of the o-ring 228 and near the outer circumference of the target212. In the illustrated embodiment, the pressure pads 240 are generallycylindrical in shape and configured to snuggly fit within the bore holes241. Desirably, there are between about 4 and 30 pressure pads aroundthe circumference of the target, and more preferably, between about 10and about 20 pressure pads. In one preferred embodiment, the pressurepads 240 have a diameter of about 0.228 inches (5.79 mm) and are about0.130 (3.30 mm) inches tall, although other dimensions may be usedwithout departing from the scope of the invention. In the embodimentusing the above-sized pressure pads, the counter bore holes 242 formedin the target 212 are desirably about 0.115 inches (2.92 mm) deep. Thisgives the pressure pads 240 about a 0.015 inch (0.381 mm) clearanceabove the surface of the outer flange of the target 212. The clearanceforms the gap G thereby substantially preventing the target 212 fromcontacting the insulating ring 226. Alternately, the spacer 240 can bean annular ring received in a groove in the target 212. Additionally,although not specifically illustrated, one skilled in the art willunderstand that spacer 240 can likewise be inserted between theinsulating ring 226 and the adapter portion 232 of the PVD chamber wall214 and that the spacer 240 may be inserted into counter bore holes inthe insulating ring instead of the target as in the illustratedembodiment.

FIG. 3 illustrates a reactor 300 with a gap G formed between target 312and insulating ring 326 using another embodiment of spacer 340. In thisembodiment, the spacer 340 comprises a spacer that is received betweenthe target 312 and insulating ring 326 and snaps into a groove 342 onthe outer circumference of the target 312. The spacer 340 may be anannular ring or may be formed by a plurality of individual spacerslocated around the circumference of the target as with the pressure padsdescribed with reference to FIGS. 2A and 2B. FIG. 4 illustrates yetanother embodiment where spacer 440 snaps over the insulating ring 426and into a groove 444 on the outer circumference of the insulating ring.

In the embodiments illustrated in FIGS. 3 and 4, the spacers desirablyhave tongue portions 348, 448 inserted between the target 312, 412 andinsulating ring 326, 426 having a width of between about 0.010 inches(0.25 mm) and 0.020 inches (0.50 mm) to form the gap G. An arm 350, 450extends from the tongue 348, 448 and has a post 352, 452 that isreceived in grooves 342, 444 by frictional fit to secure the spacer 340,440.

FIG. 5 illustrates yet another embodiment of a spacer 540 used to form agap G between a target 512 and the corresponding insulating ring 526. Inthis embodiment, the spacer 540 is a coating or tape applied to thetarget 512 with an adhesive.

While this invention has been described in conjunction with the specificembodiments described above, it is evident that many alternatives,combinations, modifications and variations are apparent to those skilledin the art. Accordingly, the preferred embodiments of this invention, asset forth above are intended to be illustrative only, and not in alimiting sense. Various changes can be made without departing from thespirit and scope of this invention.

1. A sputtering plasma reactor for plasma vapor deposition (PVD), thereactor comprising: a PVD chamber wall; a PVD target, wherein the targetand the PVD chamber wall form a vacuum chamber, and wherein at least theportion of the target facing said vacuum chamber is composed of materialto be sputtered; an insulating ring positioned between the target andthe PVD chamber wall; a first O-ring provided to establish a vacuum sealbetween the target and the insulating ring; a second O-ring provided toestablish a vacuum seal between the insulating ring and the PVD chamberwall; and at least one spacer positioned between the target and theinsulating ring, wherein each of the at least one spacer contacts boththe insulating ring and the target to provide a gap between theinsulating ring and the target.
 2. The sputtering plasma reactor ofclaim 1, wherein each of the at least one spacer is disposed within acounter bore.
 3. The sputtering plasma reactor of claim 2, wherein thecounter bore is formed into the insulating ring.
 4. The sputteringplasma reactor of claim 2, wherein the counter bore is formed into thetarget.
 5. The sputtering plasma reactor of claim 1, wherein theentirety of the at least one spacer is located between the insulatingring and the target.
 6. The sputtering plasma reactor of claim 1,wherein at least a portion of each of the at least one spacer is locatedbeyond the insulating ring and the target.
 7. The sputtering plasmareactor of claim 1, wherein the at least one spacer comprises aplurality of spacers disposed between the target and the isolation ringin a spaced-apart manner.
 8. The sputtering plasma reactor of claim 1,wherein the at least one spacer comprises a single annulus.
 9. Thesputtering plasma reactor of claim 8, wherein the single annulus isreceived in an annular groove formed into the target at a positionradially outward relative to the first O-ring.
 10. The sputtering plasmareactor of claim 1, wherein a portion of the at least one spacer issnappable into a groove formed into an outer circumferential edge of thetarget.
 11. The sputtering plasma reactor of claim 10, wherein the atleast one spacer includes a tongue portion receivable between the targetand insulating ring and a an arm extending from said tongue portion, thearm includes a post at a distal end thereof, the post being snappableinto the groove formed into the target by frictional fit to secure theat least one spacer.
 12. The sputtering plasma reactor of claim 11,wherein the tongue portion has a thickness of between about 0.010 and0.020 inches (0.25 and 0.50 mm) to form the gap between the target andthe insulating ring.
 13. The sputtering plasma reactor of claim 1,wherein a portion of the at least one spacer is snappable into a grooveformed into an outer circumferential edge of the insulating ring. 14.The sputtering plasma reactor of claim 13, wherein the at least onespacer includes a tongue portion receivable between the target andinsulating ring and a an arm extending from said tongue portion, the armincludes a post at a distal end thereof, the post being snappable intothe groove formed into the insulating ring by frictional fit to securethe at least one spacer.
 15. The sputtering plasma reactor of claim 14,wherein the tongue portion has a thickness of between about 0.010 and0.020 inches (0.25 and 0.50 mm) to form the gap between the target andthe insulating ring.
 16. The sputtering plasma reactor of claim 1,wherein the at least one spacer is a coating applied to the target withan adhesive.
 17. A sputtering plasma reactor for plasma vapor deposition(PVD), the reactor comprising: a PVD chamber wall; a PVD target having afirst sealing surface, wherein the target and the PVD chamber wall forma vacuum chamber, and wherein at least the portion of the target facingsaid vacuum chamber is composed of material to be sputtered; aninsulating ring positioned between the target and the PVD chamber wall,the insulating ring having a second sealing surface, wherein the firstsealing surface of the PVD target is positioned adjacent to the secondsealing surface of the insulating ring; a first O-ring located betweenthe target and the insulating ring to provide a vacuum sealtherebetween; a second O-ring located between the insulating ring andthe PVD chamber wall to provide a vacuum seal therebetween; and at leastone spacer positioned between the target and the insulating ring,wherein the spacer contacts the first sealing surface of the target andthe second sealing surface of the insulating ring to maintain the targetand the insulating ring in a spaced-apart relationship.
 18. Thesputtering plasma reactor of claim 17, wherein the at least one spaceris an annular ring.
 19. The sputtering plasma reactor of claim 18,wherein the annular spacer is receivable within at least one of anannular groove formed into the target and an annular groove formed intothe isolation ring.
 20. The sputtering plasma reactor of claim 18,wherein the annular groove is located radially outward of the firstO-ring.
 21. A spacer for use in a sputtering plasma reactor, the spacerbeing disposed between a target and an isolation ring attached to a wallof the reactor for providing a gap between the target and the isolationring, the spacer comprising: a tongue having a first contact surface anda second contact surface and a thickness defined by the first and secondcontact surfaces, wherein at least a portion of the first contactsurface is engageable with the target and at least a portion of thesecond contact surface is engageable with the isolation ring, and thefirst contact surface is substantially parallel to the second contactsurface.
 22. The spacer of claim 21, wherein the first and secondcontact surfaces are circular.
 23. The spacer of claim 21, wherein thefirst and second contact surfaces are annular.
 24. The spacer of claim21, wherein the thickness is about 0.130 inches (3.30 mm).
 25. Thespacer of claim 21 further comprising an arm extending transversely froman end of the first contact surface or the second contact surface of thetongue, wherein the arm is snappingly engageable with a groove formedinto an outer radial surface of the target or an outer radial surface ofthe isolation ring.